The present invention relates to methods for modifying psyllium with a psyllium modifying agent to improve and extend the functionality of the psyllium. In a preferred embodiment, the psyllium modifying agent is an enzyme. The resultant modified psyllium has improved manufacturing qualities that is prepared from raw psyllium. More particularly, the modified psyllium of the present invention has, e.g. a decreased gel hardness compared to that of the raw psyllium starting material, and in preferred embodiments a 5% w/v suspension of modified psyllium in water does not gel at all or gels to an insubstantial degree.
The present invention also relates to food products containing the modified psyllium, methods for preparing the food products, and methods treating a patient by administering the modified psyllium of the invention to the patient, e.g. to lower serum cholesterol.
Psyllium is a mucilaginous material derived from seeds from the plants of the Plantago genus, which grows in certain sub-tropical regions. Plantago ovata is a preferred species and is commercially grown in India. The seeds of Plantago sp. are dark brown, smooth, boat shaped and shiny. Psyllium seed is used in whole, ground or dehusked form to make a variety of psyllium containing products.
Starches are among the polysaccharides that naturally occur in plants, including psyllium. Starches are polysaccharides that naturally occur in grains and other plants, and serve as a permanent food store for the plant. Starch includes two structurally different polysaccharides, amylose and amylopectin. Amylose is a linear molecule composed of250-300 D-gluco-pyranose units uniformly linked by alpha-1,4 glucosidic bonds. Amylopectin consists of 1000 or more glucose units that are also connected with alpha-1,4 glucosidic bonds, but also has a number of branch attached to the main chain by alpha-1,6 glucosidic bonds.
It is known to use enzymes, particularly glucanases, to modify the starches in various farinaceous grains to obtain more desirable polysaccharides. Amylases are enzymes that hydrolyze the alpha-1,4 bonds. Alpha-amylases hydrolyze starch by random splitting of these bonds. .beta.-amylases can only hydrolyze the alpha-1,4 linkages of amylopectin until a branch point is approached because the enzyme cannot hydrolyze alpha-1,6 bonds, leaving dextrins as a byproduct. U.S. Pat. No. 5,225,219 to Inglett describes a process for producing amylodextrin compositions from the starches of various substrates, e.g. cereal grains, by hydrolysis with an alpha-amylase.
However, it is not the starches of psyllium that relate to the poor functional qualities of psyllium, but other polysaccharides such as the soluble and insoluble fibers. Psyllium husk, an excellent source of both soluble and insoluble fibers, and has a proven cholesterol-lowering effect. There are two main types of known dietary fibers broadly classified as soluble fibers and insoluble fibers. Generally, insoluble fibers are recognized for their bulk laxative effect, while soluble fibers are known to have a cholesterol-lowering effect. Psyllium seed, particularly the psyllium husk, and certain other grains, particularly oats, contain both soluble and insoluble fibers, and are commercially available in various foods and pharmaceuticals.
Psyllium seed husk has a soluble fiber content approximately eight times greater than that of the soluble fiber content of oat bran, and thus there is great interest in psyllium for its beneficial health effects. These beneficial health effects include reducing serum total cholesterol, reducing low density lipoprotein cholesterol, lowering glycemic index and lipid levels, affecting fecal and colonic microbial metabolism, and for treatment of intestinal disorders.
Psyllium contains both neutral and acidic polysaccharides. Psyllium from different Plantago species vary in monosaccharide composition and content. These monosaccharides include D-xylose, D-arabinose, D-rhamnose, D-galactose, D-galacturonic acid, 4-O-methyl-D-glucuronic acid, and 2-O-(2-D-galactopyranosyluronic acid)-L-rhamnose (1,2,3,4,5). Kennedy et al. have reported detailed structural data for Plantago ovata. See, e.g., Kennedy et al., Structural datafor the carbohydrate of ispaghala husk ex plantago ovata forsk, Carbohydrate Research 75:265-274 (1979). Methylation analysis and partial acidic hydrolysis have shown that the mucilage polysaccharide is a highly branched acidic arabinoxylan. The xylan backbone has both (1.fwdarw.44) and (1.fwdarw.3) linkages. Substitutent groups, including rabinose, xylose, and 2-O-(galactopyranosyluronic acid)-rhamnose, are attached to the arabinoxylan chain by (1.fwdarw.2) and (1.fwdarw.3) linkages.
Psyllium husk can absorb as much as 90 times its weight in water and forms a viscous gel upon hydration. These properties are problematic to the preparation of psyllium-containing products. The mucilaginous nature of psyllium leads to an undesirable slimy or adhesive texture and mouth- feel upon hydration. This slimy mouthfeel is unpalatable and various attempts have been made to mask these undesirable characteristics.
The aforementioned difficulties become particularly troublesome when formulating beverages or drink mixes. Leis, Jr. and others have attempted to overcome some ofthe problems associated with a bulk laxative powdered drink mix preparation by using a raw psyllium having a specific particle size range as described in U.S. Pat. Nos. 5,445,831 and 5,149,541.
Barbera et al. describe the inclusion of an amount of an edible acid, e.g. citric acid, high enough to slow the gelation rate but below a level that the edible acid is a flavorant to prevent agglomeration ofpsyllium of aparticularparticle size range, e.g. as described in U.S. Pat. Nos. 5,234,687, 5,219,570 and 5,425,945.
U.S. Pat. No. 4,551,331 and its U.S. Reissue No. 32,811 describe a modified dry dietary fiber product, wherein a dietary fiber such as psyllium is coated with from 0.5 to 20% by weight of a food grade emulsifier. U.S. Pat. Nos. 44,459,280 and 4,548,806 to Colliopoulos et al. also attempt to alleviate agglomeration caused by psyllium gelation by coating psyllium with a hydrolyzed starch oligosaccharide such as maltodextrin, which may also function as an emulsifying agent.
It is known that several other variables can be controlled to inhibit psyllium hydration. These variables include formation of nuggets by extrusion as described in U.S. Pat. No. 5,227,248. Changes in pH or particle size, competition of other food ingredients for water (e.g. sugar), or addition of citric acid have previously been used to improve the handling properties of psyllium.
Additionally, the U.S. Food and Drug Administration (USFDA) requires a considerable amount of psyllium must be included in a food product before a health claim can be made for reducing serum cholesterol, i.e. the amount of psyllium to be included is generally about 10 g/day, which provides approximately 7 g of soluble fiber/day.
Drink mixes are apreferred psyllium delivery system, but suitable drink mixes containing such an amount of psyllium cannot be made using raw psyllium. Therefore, psyllium containing beverages generally deliver 3.4 g of psyllium, approximately one-third ofthe required daily dose. Therefore, the consumer must imbibe three 8 oz. psyllium-containing beverages/day to ingest the required daily dose.
It has been widely accepted that pH can alter the functionality of a polysaccharide by influencing the molecular charges. The changes ofmolecular charges subsequently influence the interactions between solutes and lead to an alteration of food functionality. It has been shown that the rate of psyllium hydration in a psyllium-containing suspension can be reduced by adjusting the pH of a psyllium-containing suspension. The influence of particle size on the polysaccharide hydration has also been established. Similar to most polysaccharides, psyllium with a smaller particle size has a greater hydration rate. The competition of other ingredients, such as salt and sugar, have been observed to reduce psyllium polysaccharide hydration, including the polysaccharides found in psyllium.
Difficulties notwithstanding, the desirable therapeutic effects provided by psyllium have led to many prior art psyllium-containing formulations. For example, various psyllium-containing foods have been proposed which purport to take advantage of the natural digestion regulation properties of psyllium, or the satiating effect of psyllium, e.g. as described in U.S. Pat. Nos. 3,574,634 and 4,348,379. U.S. Pat. No. 5,266,473 describes the enzymatic treatment of psyllium with certain proteases to alleviate problems associated with psyllium allergenicity.
There is a need in the art to overcome the manufacturing and handling difficulties associated with psyllium. The present invention relates to enzymatically treated psyllium and is described in detail below.